In recent years, light sensitive materials for color print paper have been so demanded as to be rapidly processed for the purpose of expediting the deliveries of a large quantity of prints. As one of the techniques for accomplishing the purpose, there have been the known attempts for making a color development rapid by making use of a silver chloride emulsion or a silver chlorobromide emulsion having a high silver chloride content as a silver halide emulsion to be used in the light sensitive materials for color print paper. The above-mentioned techniques are described in, for example, U.S. Pat. Nos. 4,183,756 and 4,225,666 and Japanese Patent Publication Open to Public Inspection (hereinafter abbreviated to as JP OPI Publication) Nos. 55-26589/1980, 58-91444/1983, 58-95339/1983, 58-94340/1983, 58-95736/1983, 58-106538/1983, 58-107531/1983, 58-107532/1983, 58-107533/1983, 58-108533/1983 and 58-125612/1983.
However, the above-mentioned silver chloride emulsion or silver chlorobromide emulsion having a high silver chloride content has had the defects that the photosensitive speed is low and the reciprocity law failure is large, namely, the photosensitive speed and gradation are seriously varied by exposure illuminance. For solving the above-mentioned defects, there have been various attempts. For example, JP OPI Publication Nos. 51-139323/1976 and 59-171947/1984 describe each that a processing stability and reciprocity law failure characteristics can be improved by containing the metal compounds belonging to Group VIII of Periodic Table in a light sensitive material.
In the techniques disclosed therein, however, it has been not satisfactory to solve the above-mentioned problems of the silver chloride or the silver halide having a high silver chloride content. In the meanwhile, JP OPI Publication No. 1-183647/1989 describes that, when iron ions are contained in silver halide having both of a silver bromide containing phase having a high silver bromide content and a high silver chloride content, a photosensitive speed can be increased, the reciprocity law failure characteristics can be improved, and the photosensitive speeds and gradations varied by the temperatures varied by exposing a light sensitive material to light can also be improved.
However, the technique still has another serious problem in latent image stability that a photosensitive speed is seriously varied by the intervals between an exposure and a processing treatment, though the above-mentioned problems may nearly be solved. Besides the above, JP OPI Publication No. 55-135832/1980 describes that a high-speed emulsion can be prepared by doping cadmium, lead, copper or zinc therein. According to the studies made by the present inventors, it was proved that this technique cannot make a photosensitive speed higher and improve the reciprocity law failure at the same time satisfactorily. JP OPI Publication No. 2-20852/1990 discribes on a silver halide emulsion containing the complexes of a transition metal having a nitrosyl or thionitrosyl ligand, but not particularly describes on any increase of photosensitive speeds. Further, JP OPI Publication Nos. 2-20853/1990 and 2-20855/1990 describe on the complexes having each a cyano ligand which are capable of making a photosensitive speed higher. However, when these complexes are used, there is a serious environmental problem, because the cyano ligands are severely toxic and it is further proved to be unsatisfactory to make any photosensitive speeds higher and to improve any reciprocity law failure characteristics.